In recent years, use of a transparent plastic film as a substrate instead of a glass sheet has been proposed for displays (e.g., liquid crystal display and electroluminescence (EL) display) in order to implement a reduction in thickness, a reduction in weight, an increase in flexibility, and the like.
However, since a plastic film tends to allow water vapor, oxygen, and the like to pass through as compared with a glass sheet, the elements provided in a display tend to deteriorate.
In order to solve this problem, Patent Document 1 proposes a flexible display substrate in which a transparent gas barrier layer formed of a metal oxide is stacked on a transparent plastic film.
However, since the transparent gas barrier layer formed of a metal oxide is stacked on the surface of the transparent plastic film by evaporation (deposition), ion plating, sputtering, or the like, cracks may occur in the gas barrier layer when the substrate is rolled up or bent, and the gas barrier capability may deteriorate. Moreover, since a solid raw material is used as the target, the raw material cost increases.
Patent Document 2 discloses a gas barrier laminate that includes a plastic film, and a resin layer that contains a polyorganosilsesquioxane as the main component and is stacked on at least one side of the plastic film.
However, since it is necessary to further stack an inorganic compound layer in order to obtain a gas (e.g., oxygen and water vapor) barrier capability, the process becomes complicated, and the production cost increases. Moreover, toxic gas may be used.
Patent Document 3 discloses a method for producing a gas barrier film wherein a thin film that contains silicon oxide as the main component is formed on a polymer film using a CVD method that utilizes plasma generated at a pressure of 600 to 1520 Torr using an organosilicon compound that is liquid at a temperature of 20 to 150° C. as a deposition raw material.
However, the gas barrier film obtained by the method disclosed in Patent Document 3 exhibits an insufficient gas barrier capability.
Patent Document 4 discloses a transparent gas barrier laminate film that is obtained by sequentially stacking a silicon oxide layer having a high degree of oxidation and a silicon oxide layer having a low degree of oxidation on a base using a dry coating method, subjecting the surface of the silicon oxide layer having a low degree of oxidation to a plasma treatment using oxygen gas or the like, and stacking a polymer layer on the plasma-treated surface of the silicon oxide layer having a low degree of oxidation.
However, since it is necessary to stack a plurality of layers in order to obtain the gas barrier laminate film, the production process is complex and economically disadvantageous.